I think the problem may be that the blue border is stacked in front of the text boxes, making it initially impossible to click on anything below the transparent area in the centre of the border. (Unless there's a way of 'clicking through' which I'm not aware of.)
Before I could edit the text, I had to
a) Click the blue border to select it
b) Go to the Arrange menu and choose Unlock (the crosses in the corners then become boxes).
c) With the border still selected, go to the Arrange menu again and choose Send to Back.
d) You can now click on, and edit, the text boxes which were originally below the transparent area of the border image and thus unclickable.
Once you've edited the text, you can select the border, go to the Arrange menu and choose Bring to Front so that the small 'notches' on the inside of the border appear above the fawn background.
Hope this helps,
H